The connector industry is moving towards an environment where virtually any device may be powered over a network using an ethernet cable. Previously, such power requirements reached as high as 15 watts. Now standards are requiring that ethernet cables and corresponding connectors handle as much as 30 watts. In a typical RJ45 type connector assembly where a modular plug mates in a male-female relationship with a jack, an isolating magnetic device is used in the connector to handle direct current (“DC”) offsets. Such offsets may be caused by various factors including imbalances in the wires of the plug.
For example, data is frequently transmitted over a pair of conductive wires. When transmitting data, the pair of wires may ideally have voltage potentials to ground such that a voltage in one wire of the pair is equal and opposite to the voltage in the other wire of the pair. For example, one wire may have a potential of −2.5 volts and the other wire may have a potential of +2.5 volts. If there are imbalances in the pair of wires or extraneous electro-magnetic interference, the two wires may not have exactly equal and opposite voltages. For example, one wire may have −2 volts and the other wire may have +3 volts. Although there is still a net difference across the pair of wires of +5 volts (which may, for example, correspond to a logic “1”), such a voltage imbalance will generate a current imbalance. Conventional technology uses isolating magnetic devices to deal with such imbalances. However, prior art magnetic devices cannot physically handle the magnetizing force which may be induced by imbalanced DC current having a power complying with the power requirements of new standards. If the transformer is not capable of handling such imbalances, the transformer may saturate and data may not transmit from one side of the transformer to the other. For example, prior art transformers are able to handle low tolerances such as 8 mA of DC current bias and the corresponding power such current produces. Now, industry standards are requiring that isolating magnetics handle 24 mA and as much as 34 mA of DC current bias. For example, the IEEE 802.3 AN standard requires such current bias tolerance. Prior art transformers are generally not capable of handling such currents and power.
As an illustrative example, referring to FIG. 1, there is shown a transformer 40 in accordance with the prior art. Transformer 40 may be used as an isolating magnetic device. Transformer 40 is formed by winding wires 44, 46, 48 and 50 around a toroid shaped core 42 formed of a conductive material. Core 42 has a substantially circular cross-section. Wires 44, 46, 48 and 50 are evenly wound around core 42 except in a gap area 38. As discussed above, when a high power DC current bias is added onto an alternating current and applied to one side of transformer 40, the entire core of transformer 40 may become saturated from the induced magnetic flux. Such saturation inhibits transfer of data in the alternating current component. Some attempts to compensate for this problem in the prior art include using a larger core 42. However, use of a larger core is not practical in many applications including connector applications due to space limitations.
Therefore, there is a need in the art for an electric device which can handle higher power DC current bias than transformers available in the prior art and a method for manufacturing such a device.